I recall him being more aggressive during summer league. I think the Jazz coaching staff is being very cautious about what they ask him to do, particularly during the early part of the season. It's in no one's best interest to see their hopeful star player get body-checked into the 3rd row by players like Andre Drummond and Marc Gasol. This is still a re-build year.
https://www.youtube.com/watch?v=EiOLIB9pF2Y
https://www.youtube.com/watch?v=EiOLIB9pF2Y